Egress fees are the per-gigabyte charges a cloud provider levies on outbound traffic leaving its network. Inbound traffic is almost always free; outbound is typically billed at $0.05–$0.12 per GB on the major US hyperscalers, with steep tiered discounts that only apply at hundreds of TB/month. The asymmetry is deliberate — egress fees are a structural lock-in mechanism that punishes data migration and multi-cloud architectures, and they are the dominant unexpected line item on most cloud bills.

In a self-hosting context

Self-hosting on a flat-rate VPS is the cleanest hedge against egress surprises: most VPS plans bundle 10–20 TB/month of outbound traffic for free, and Hetzner (and the other providers in VPS providers compared) charge $1–$2 per TB once you exceed it — orders of magnitude cheaper than AWS S3 or any hyperscaler equivalent. For backup workloads, this is exactly why a self-hosted S3-compatible object store on bandwidth-bundled VPS hardware (MinIO, Garage, SeaweedFS) usually wins on total cost of ownership.